[UlisesGascon]

⚠️ Breaking changes

• The env setting is no longer derived from NODE_ENV and now defaults to production, so the safe behavior is the default: the default error handler never includes error details in responses and view cache is enabled. Set app.set('env', 'development') to get the previous development behavior, or set view cache directly

  const app = express();
  app.get('env'); // => 'production', regardless of NODE_ENV
  app.set('env', 'development'); // opt in to error details in responses
  app.set('view cache', false); // opt out of template caching

Notes for reviewers

• The test suite previously relied on NODE_ENV=test. test/support/env.js now defaults every app to env: test by wrapping defaultConfiguration, which keeps error details in test responses and the default logger quiet. Explicit app.set('env', 'test') calls in the affected tests would be the alternative.
• Exploratory PR for the 6.x line, parked until the major is consolidated.

[UlisesGascon]

If we agree on this approach... then I can prepare a deprecation warning for express@5